I think you guys are missing the point. The fact that he looks like a kid, has a short temper, and doesn't fully seem to know what he's doing was carefully thought out when they created his character. He's meant to be this conflicted vader fanboy with an ego and something to prove. Ren's hatred isn't fueled by power or anger, it's driven by fear--fear that he will never live up to vader or that all his learning will be for nothing.